Hydraulically operated disc brakes



Dec. 7, 1965 J. w. DAVIS ETAL HYDRAULICALLY OPERATED DISC BRAKES 2Sheets-Sheet 1 Original Filed May 1, 1963 F/GJ.

FIG .2.

Ur. ov a v.5

Dec. 7, 1965 J. w. DAVIS ETAL HYDRAULIGALLY OPERATED DISC BRAKES 2Sheets-Sheet 2 Original Filed May 1, 1963 I wexT. 0115 wctwm gs UnitedStates Patent HYDRAULICALLY OPERATED DISC BRAKES John Walter Davis,Birmingham, and Kenneth John Wells,

Castle Bromwich, England, assignors to Girling Limited,

Birmingham, England, a British company Continuation of application Ser.No. 277,273, May 1,

1963. This application Feb. 11, 1965, Ser. No. 448,198 2 Claims. (Cl.188-152) This invention relates to improvements in hydraulicallyoperated disc brakes of the kind in which friction pads are applied toopposite faces of a disc rotating with a vehicle wheel by pistonsworking in opposed hydraulic cylinders in a fixed caliper whichstraddles a portion of the disc; and this application is a continuationof our prior application Serial No. 277,273, filed May 1, 1963.

The disc is usually mounted on the inboard side of and close to thewheel.

In all hydraulic systems it is essential to ensure that the system iscompletely filled with liquid and any air in the system has to be bledoil? through external bleed screws.

It is known to feed hydraulic fluid into a cylinder in one limb of thecaliper and to provide an internal passage in the caliper which connectsthis cylinder to a cylinder in the second limb of the caliper, thepassage communicating with a bleed screw. Hydraulic fluid fed into thecylinder in the first limb first fills that cylinder and then overflowsthrough the passage into the cylinder in the second limb, from which theair is driven through the bleed screw. This arrangement has thedisadvantage that, when the system is being filled, air in the secondcylinder cannot pass freely to the bleed screw, because its flow isimpeded by liquid flowing from the first to the second cylinder.

This disadvantage is avoided by the present invention according to whichthe bleed screw is connected to the outer end of the cylinder in thesecond limb by an independent pipe or passage. The passages between thebleed screw and the cylinders may be arranged in various ways.

Some of these are illustrated by way of example in the accompanyingdrawings in which:

FIGURE 1 is an end elevation of a brake caliper,

FIGURE 2 is a side view of the caliper, and

FIGURES 3, 4 and 5 are sections of the caliper on the line 3-3 of FIGURE2 showing various ways of arranging the internal passages.

The caliper illustrated is formed in two complementary halves 10, 11secured together by bolts 12, the joint being in the central plane ofthe disc with which the caliper co-operates. A union 13 to receive apipe from a master cylinder is located on the limb of the caliper whichis on the inboard side of the disc when the caliper is in position, apassage leading from the union into the hydraulic cylinder 14 in thatlimb. Inclined bores 15, 16 are drilled from the meeting faces of thetwo halves of the caliper into the outer end of the cylinder 14 and theouter end of the cylinder 17 in the other limb of the caliper. The innerends of the passages register and one face is recessed as shown at 18 toreceive an annular seal.

A bleed bore 19 of smaller diameter than the bores 15, 16 is drilled inthe inboard limb 10 of the caliper substantially parallel to the axis ofthe disc. The inner end of this passage meets the inner ends of thepassages 15, 16 and its outer end is normally closed by a bleed screw21.

The angular disposition of the passages 15, 16 is conveniently such thatthey communicate with the outer ends of the cylinders at points abovethe axes of the cylinders and the passages are inclined upwardly towardstheir junction and towards the inner end of the bleed passage 19 asshown in dotted lines in FIGURE 2.

3,221,844 Patented Dec. 7, 1955 In the embodiment shown in FIGURE 3 atube 22 of small bore extends from the bleed passage 19 through thepassage 16 to its junction with the cylinder 17. Thus, when filling thesystem with liquid through the union, air from the cylinder 14 andsurplus liquid from that cylinder flows into the cylinder 17 through thepassages 15, 16 and the air is discharged through the tube 22 and thebleed passage 19, filling being continued until liquid free of air comesfrom the bleed screw.

From the above description it will be apparent that the first limb 10 ofthe caliper has an inlet connection 13 for liquid to its cylinder 14, anoutlet connection 15 for liquid from its cylinder 14, and a bleedconnection 19, and the second limb 11 of the caliper has an inletconnection 16 for liquid to its cylinder 17, and an outlet connection 22for liquid from its cylinder 17, the outlet 15 from said first limbbeing connected to the inlet 16 of the second limb and the outlet 22from the second limb leading into the bleed connection 19 of the firstlimb.

In the modification shown in FIGURE 4 one end of a tube 23 is crankedand flared to fit into the outer end of the passage 15, and the tube,which is of smaller diameter than the passage 16, extends through thatpassage to its junction with the cylinder 17. Thus air and liquid fromthe cylinder 14 are delivered through the passage 16 and the tube 23into the cylinder 17 and the air from both cylinders flows out throughthe passage 16 around the tube 23 and through the bleed passage 19.

In this arrangement the tube 23 forms the inlet connection to thecylinder 17 in the second limb 11 of the caliper and the passage 16forms the outlet connection from the cylinder 17 leading into the bleedconnection 19.

In the modification shown in FIGURE 5 the passage 16 is dividedlongitudinally by a partition 24, the part of the passage on one side ofthe partition being in communication with the passage 15 and thecylinder 17, and the part on the other side connecting the cylinder 17with the bleed passage 19.

In this arrangement a part of the passage 16 on one side of thepartition 24 forms the inlet connection to the cylinder 17 in the secondlimb 11 of the caliper and the part on the other side of the partitionforms the outlet connection from the cylinder 17 leading into the bleedconnection 19.

We claim:

1. A hydraulic disc brake of the kind in which friction pads are appliedto opposite faces of a disc rotatable with the vehicle wheel by pistonsworking in fixed cylinders in the limbs of a fixed caliper whichstraddles a portion of the disc, said caliper comprising twocomplementary halves bolted together, the two bores drilled from themeeting faces of the two halves to the outer ends of the cylinders, athird bore closed by a bleed screw drilled in one half to meet one ofthe two bores, an inlet means through which liquid is fed into acylinder in one limb of the caliper and means forming two passageswithin the bore in the other limb of the caliper, one of said passagesextending between the outer end of the cylinder in said other limb andthe bore in the first limb and the other of said passages extendingbetween the outer end of the cylinder in said other limb and said thirdbore.

2. A hydraulic disc brake of the kind in which friction pads are appliedto opposite faces of a disc rotatable with a vehicle wheel by pistonsworking in the limbs of a fixed caliper which straddles a portion of thedisc, the said caliper comprising first and second parts securedtogether and respectively incorporating first and second hydrauliccylinders, two bores one in each part, extending from the 3 4 meetingfaces of the two parts to the cylinders, a third References Cited by theExaminer bore in said first part normally closed by a bleed screw andUNITED STATES PATENTS meeting one of said two bores, an inlet meansthrough which liquid under pressure is fed to said first cylinder,2,957,553 10/1960 choufngs et a1 and means forming two passages withinthe bore in said 5 3077954 2/1963 Ihnaclk 188-218 second part, one ofsaid passages within the bore extend- FOREIGN PATENTS in between saidsecond cylinder and the bore in the first pa rt and the other of saidpassages extending between 1,281,582 12/1961 France' said secondcylinder and the third bore. MILTON BUCHLER, Primary Examiner.

2. A HYDRAULIC DISC BRAKE OF THE KIND IN WHICH FRICTION PADS ARE APPLIEDTO OPPOSITE FACES OF A DISC-ROTATABLE WITH A VEHICLE WHEEL BY PISTONSWORKING IN THE LIMBS OF A FIXED CALIPER WHICH STRADDLES A PORTION OF THEDISC, THE SAID CALIPER COMPRISING FIRST AND SECOND PARTS SECUREDTOGETHER AND RESPECTIVELY INCORPORATING FIRST AND SECOND HYDRAULICCYLINDERS, TWO BORES ONE IN EACH PART, EXTENDING FROM THE MEETING FACESOF THE TWO PARTS TO THE CYLINDERS, A THIRD BORE IN SAID FIRST PARTNORMALLY CLOSED BY A BLEED SCREW AND MEETING ONE OF SAID TWO BORES, ANINLET MEANS THROUGH WHICH LIQUID UNDER PRESSURE IS FED TO SAID FIRSTCYLINDER, AND MEANS FORMING TWO PASSAGES WITHIN THE BORE IN SAID SECONDPART, ONE OF SAID PASSAGES WITHIN THE BORE EXTENDING BETWEEN SAID SECONDCYLINDER AND THE BORE IN THE FIRST PART AND THE OTHER OF SAID PASSAGESEXTENDING BETWEEN SAID SECOND CYLINDER AND THE THIRD BORE.